WASHINGTON, DC - JUNE 25: FILE, Former Presidential aide John Dean III on waiting to testify with Mrs. Dean at his side on June 25, 1973 in Washington, D.C. (Photo By James K. W. Atherton/The Washington Post via Getty Images)

If he had it to do all over again, John Dean admits that he wouldn't have embarked on the four years of work that it took to complete "The Nixon Defense: What He Knew and When He Knew It" (Viking, $35).

"I didn't know that I would have to transcribe all of those tapes. Had I known that, I would have said, `You're insane,' " the former legal counsel to President Richard Nixon said in a recent interview of what he initially thought would be a much simpler project designed to mark next month's 40th anniversary of Nixon's resignation on Aug. 9, 1974.

Dean will be launching his national book tour with an appearance at the Greenwich Library on publication day, Tuesday, July 29.

"I was looking to figure out a few key decisions ... (such as) how could he have said he didn't know (about the June, 17, 1972, Watergate break-in) until March (1973)?," Dean said of putting together a book about Nixon's doomed response to Watergate.

As he pulled together the material he needed, Dean realized that the answers to a lot of the questions he wanted to ask were in the hundreds of hours of untranscribed White House Watergate discussions held by the National Archives and Records Administration in Washington, D.C.

Less than half of the roughly 1,000 Watergate conversations captured on Nixon's recording system had been transcribed in the lead-up to the president's resignation. Once Nixon left office, the urgency of finding out what was on the rest of the tapes vanished, and they sat in the NARA vaults until Dean came along decades later.

Dean was there at the time and able to recognize the voices of all of the players, so he thought the best bet would be to do the transcribing himself -- until he realized how mind-boggling the size and difficulty of the task was. "Because of the poor sound quality, transcribing Nixon's recordings is extremely arduous and time consuming, sometimes not even possible. It can take many hours to transcribe less than a minute of conversation," he writes in the book.

Through a friend at California State University at San Bernardino, Dean recruited a team of graduate students who wound up doing the bulk of the painstaking listening and typing. Even with that help, however, the project was so big and complicated that the book nearly missed its deadline.

As the new transcripts were assembled, the author faced the equally arduous task of presenting the material in a lucid, chronological account of the historic scandal, from the bungled break-in at the Democratic campaign headquarters at the Watergate, through the cover-up by Nixon and his associates and the subsequent two-year drama that led to the president's resignation.

Dean was one of many Nixon administration figures who served jail time due to their involvement in the Watergate scandal. By agreeing to be a key witness, however, he received a reduced sentence of four months. The fallen Nixon staffer went on to write one of the earliest and most successful books about Watergate, "Blind Ambition," and a subsequent career as a lecturer and author of well-received volumes on other presidents, including Warren G. Harding and George W. Bush. He and his wife, Maureen, live in Beverly Hills, Calif.

"The Nixon Defense" is full of dramatic revelations, including the realization early on by Nixon and his associates that the Federal Bureau of Investigation's assistant director Mark Felt had to be a major source for the Washington Post reporting team of Bob Woodward and Carl Bernstein. The secret of the identity of "Deep Throat" was kept from the public by Woodward until after Felt's death in 2008.

"(The term) `Deep Throat' hadn't been invented yet, but the fact that he was (a major) leaker didn't surprise me. He was known as `the white rat,' " Dean said of the term Nixon and his associates used for the man they knew was sharing secrets with their enemies at the Washington Post.

In one scene in the book, then-White House chief of staff H.R. (Bob) Haldeman tells his outraged boss, "You can't say anything about this, because it will screw up our source, and that's a real concern. (Attorney General) John Mitchell is the only one who knows this, and he feels very strongly that we better not do anything, because if we move on him, then he'll go out and unload everything. He knows everything that's to be known in the FBI."

Haldeman floated the idea of having Felt transferred to "Ottumwa, Iowa," but Nixon feared that if that happened, Felt "might go out and write a book," according to Dean.

In the subsequent mythology surrounding Watergate -- including the Oscar-winning 1976 film "All the President's Men" -- Woodward provided clues to the identity of the legendary source that led people to guess he might have been anyone from Henry Kissinger to Alexander Haig (who took over the White House chief of staff post in 1973 after Haldeman was forced to resign).

Dean is still puzzled by the "Deep Throat" revelations that continued in the Woodward and Bernstein stories until November, 1973, despite the fact that Felt left the F.B.I. in May of that year.

When I asked Dean about the big surprises for him in the new transcripts, he said, "That was endless. I was surprised that (Nixon's) only sources of information for the first eight months (after the break-in) were Haldeman and (presidential assistant John D.) Erlichman and that they weren't being square with him. He asks questions and they give him false information. It was so unlike them to be less than honest with him."

Dean was also startled by a section in the tapes where Nixon talks about giving an ambassadorship to Republican businessman and major campaign contributor Tom Pappas.

"It's like a scene from `The Godfather.' Pappas talking in his husky, whispery voice ... and Nixon selling an ambassadorship to raise money. He knew that was illegal," Dean said.

Although President Bill Clinton would face an impeachment trial in the Senate in 1998 rather than resign as Nixon did in 1974, Dean said the big difference between the two cases is that Clinton assumed he would not be convicted and Nixon knew he might lose that fight.

"The impeachment part is easy. ... You can impeach a ham sandwich, but (the Clinton case) was very political and they knew they couldn't convict him in the Senate. Nixon didn't know that," Dean said.

No one in the country was more relieved by the president's decision 40 years ago than his former legal counsel.

"I was delighted that he didn't go to trial because I would have been the central witness, and I did not look forward to that," he said.

With the work on "The Nixon Defense" continuing until just days before the book's deadline, Dean is feeling a mixture of accomplishment and exhaustion.

When I asked the 75-year-old author if he felt up to the rigors of a two-week, cross-country book tour, Dean laughed. "That's going to be a vacation," he said.

John Dean will talk about "The Nixon Defense" on Tuesday, July 29, at 7 p.m. at the Greenwich Library, 101 W. Putnam Ave., Greenwich. Doors will open at 6:30 p.m. for the free event. Visit www.greenwichlibrary.org.